Predictive accuracy of the Kristersson/Olsen formula after lung resection: a prospective study comparing minimally...

Surgical resection remains the gold standard for early-stage lung cancer. This study aimed to evaluate the predictive accuracy of the Kristersson/Olsen formula for postoperative lung function in patients undergoing minimally invasive surgery (MIS).

Seventy-five patients who underwent anatomical lung resection for lung cancer between January 2022 and January 2024 were prospectively analyzed. Preoperative, first postoperative week and second postoperative month pulmonary function test values (FEV₁, FVC), surgical approach, postoperative complications, and demographic and clinical variables were recorded.

Regardless of surgical approach, the Kristersson/Olsen formula predicted a mean postoperative FEV₁ loss of 571 mL. However, the actual mean loss in the first postoperative week was significantly greater (698 mL; p = 0.013). In the MIS group, the predicted loss was 549 mL, whereas the observed first week loss reached 750 mL (p = 0.025). In contrast, during the second postoperative month, the overall patient cohort demonstrated a significantly smaller FEV₁ loss than predicted (449 mL vs. 571 mL; p = 0.002). Similarly, MIS patients showed an actual loss of 408 mL compared with the expected 549 mL (p = 0.013). When postoperative respiratory function recovery was examined, FEV₁ and FVC losses were significantly greater at the first postoperative week than at the second postoperative month in the MIS group, with a large effect size (p < 0.001, Cohen's d 0.892 and 1.042, respectively). Thoracotomy patients also demonstrated greater early losses, with moderate-to-high effect sizes (Cohen's d: 0.586 and 0.797). Recovery of pulmonary function from the first week to the second month was more pronounced in the MIS group.

The Kristersson/Olsen formula demonstrated limited accuracy in predicting postoperative pulmonary function during the early recovery phase (up to the second postoperative month), particularly in patients undergoing minimally invasive surgery. MIS is associated with lower-than-predicted functional loss, fewer complications, and greater pulmonary recovery, suggesting that patients with limited respiratory reserve may still be suitable candidates for surgery.